The present invention relates to a novel device intended to permit the regular and continuous release of chemical substances, meaning also medicaments, and this, over a very long period, the release of the active substances following a predetermined kinetic effect from an insoluble polymeric matrix to a liquid medium which can be, particularly, that of an animal or human organism.
Very many systems are known which permit the regulated and programmed release of pharmaceutically-active substances.
These are all solid or semi-solid systems, of the type, for example, of tablets or suppositories whose composition is defined so as to result in a slow disintegration of the system, the disintegration itself being produced, either by a purely mechanical effect or by partial solubilization by the liquid medium, for example, body fluids of one or several components forming the system.
It is also known to disperse the active principle in a solid support and to produce its programmed release by diffusion through such a support.
In this case also, the systems described are numerous:
so-called semi-permeable systems are known in which the active agent (dissolved, suspended or emulsified in an inert vehicle) diffuses through a permeable membrane;
composite systems are also known in which the active agent diffuses from a more or less porous solid support, constituted by a matrix based on polymers or copolymers.
Whatever the system selected, the speeds of release are only maintained over a very short period of time and hence do not lend themselves to prolonged use.
In particular, in the veterinary field, the repeated administration of medicinal substances runs up against both economic and technical problems when animals, for example, are very numerous or dispersed in pastures.
Also, various devices have been designed so as to permit activity over a prolonged period, and, in particular, as medicinal release systems in ruminants.
Thus, there have been described, for example:
a medicament with a prolonged delayed reaction characterized in that it is in the form of a parallelepipedic article about 7 to 8 cm long and weighing about 10 to 60 g (Fr. P. 2 461 495). However, the life span of such a device hardly exceeds some days;
a device designed for continuous and regulated administration of a chemical substance, characterized in that it is formed from a reservoir of heavy material, for example, a metal cylinder provided at one of its ends with a porous wall (for example a semi-permeable membrane) through which said chemical substance diffuses (cf. French Pat. No. 2 425 242). Such a device, even if it completely fulfils the role of a longterm diffuser (two to three months), has however two important drawbacks:
the diffusion surface is very small, resulting in a low and insufficient concentration of active substances on the one hand and frequent clogging on the other hand.